The United States warned Moscow of “catastrophic consequences” if it uses nuclear weapons in Ukraine after Russia promised protection to Ukrainian regions it might annex following widely criticised referendums. 

Citizens in four regions of Ukraine were voting for a fourth day on Monday in the Russian-organised referendums that Kyiv and the West have branded a sham. They say the outcomes are pre-determined and even countries with close ties to Moscow such as Serbia and Kazakhstan say they will not recognise the results. But by incorporating the four regions – Luhansk and Donetsk in the east and Zaporizhzhia and Kherson in the south – Moscow could portray Ukraine’s efforts to retake them as attacks on Russia itself, a warning to Kyiv and its Western allies.